GCSE (9-1) Computer Science
Mark Scheme
J277/02: Random Number Generation
Question Answer Marks Guidance
1 1. random
2. 1
3. 6 		3
Python requires import random. Range must be 1 and 6.
2 Any two from:
  • Computer Games / Simulations (e.g. weather sim)
  • Cryptography / Security (generating keys)
  • Modelling (e.g. financial markets)
 2
"Games" is the most common correct answer.
3a 1 1
3b 5 1
Critical: OCR ERL and Python randint are inclusive. "4" is incorrect.
4a A new random number is generated for each if/elif check (1). It is possible for every check to be False if different numbers are rolled sequentially (1). 2
The Re-Roll Trap: Must explain that the number changes/regenerates.
4b num = random.randint(1, 3)
if num == 1 then print("Yes")
elif num == 2 then print("No")
else print("Maybe") 		3
BP1: Assign to variable once at start. BP2: Use variable in checks.
5 num = random.randint(0, 1)
if num == 0: print("Heads")
else: print("Tails") 		4
BP1: Generate random. BP2: Selection. BP3: Heads output. BP4: Tails output.
6 import random
index = random.randint(0, len(students) - 1)
print(students[index]) 		6
BP2: Calculate length (len). BP4: Correct handling of "Out of Bounds" (-1).
OCR 2026